Four people have been rushed to hospital after an accident in Carabooda.

Deputy Commissioner Stephen Brown said crime usually dropped off significantly in winter, began to rise by September and peaked in summer. But this July it was at summer levels.

In July 2015, the total number of crimes reported in the metropolitan area rose 19.6 per cent on what was reported in July 2014. This meant 300 more offences than at this time last year.

Homicide, arson and sexual assaults were either static or down but all other types of crime had risen.

The most dramatic increases were in robberies on businesses (up 36 per cent) domestic assaults (34 per cent) and threatening behaviour (26 per cent).

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Of offences "against the person", the biggest increases were in thefts (up 21 per cent) car thefts and home burglaries (each up 18 per cent).

"We have found this out in the past 36 hours ... here we are, telling you straight away, telling the community what we're doing about it," deputy Commissioner Brown said.

"We don't know why this is happening at this point in time, but we are acting now ... rather than wait until we fully understand."

The deputy commissioner has approved three-month Operation Sweep, focusing on the people and places most responsible for the rise in statistics.

He said the formation of Frontline 2020, the new police operating model, had the flexibility to rapidly divert more than 1000 officers across Perth at any time to to apply pressure where necessary without impacting day-to-day services.

The deployment will not deplete "response teams" that attend emergency calls, he said.

Organised Crime will continue to disrupt the supply of methamphetamine, or ice, into communities as part of the recently-announced state plan.

The deputy commissioner said analysts were examining the reasons for the spike but it was too early to fully understand what was driving the change.

"The crime environment is changing and that should be clear to everybody," he said.

"It is changing not only in numbers but in makeup and it is complex and there are many different drivers.

"We've talked in recent weeks about the impact of methamphetamine but there are many different factors at play and many are still unknown."

Deputy Commissioner Brown said there was no doubt ice was one of the drivers in the increased armed robberies but changes and increasing tensions in family life - including FIFO life and abuses of other substances such as alcohol - were all contributors to crime and arresting people did not address these.

He said early evaluation of the new policing model showed data that there were 10 per cent more cars available for tasking at any given time compared to this time last year.

Arrests were up 11 per cent and arrests of repeat priority offenders were up 41 per cent.

"Our police are working particularly hard, harder than ever before. And we're getting better outcomes on the road," he said.

"That's the confounding thing ... despite all of that effort, extra resourcing by police, extra application of all the things the community would expects we would be doing at this point in time, there has been this unseasonal change.

"However, we are absolutely committed to doing everything we can to stem this."

Of all offences reported, the vast majority related to theft and property damage and he urged the community to secure homes, attend to security and watch where their wallets, purses and handbags were – to make sure, in short, they were not sitting in plain view in an unattended car.

"Criminals are largely opportunistic and that's where we need the public to play their part," he said.

The community could expect to see more police on the ground and they would be supported by detectives, Regional Operations Group and other specialist teams.

Keep up with the actions of your local police through following them on Facebook or Twitter and using the hashtag #operationsweep.